For 13 years, this project has concentrated on the elucidation of renal and neuroendocrine function and disease, largely through the use of animal models with inherited forms of diabetes insipidus. The objectives outlined in the present proposal are outgrowths of our prior work in this area. The project centers about the renal countercurrent system on the one hand, and the hypothalamo-neurohypophysial system which produces principles that influence the countercurrent mechanism, on the other. The project can thus be divided into two major segments, renal and neuroendocrine, and specific objectives for the next five years include the following. In the renal category, we will look at: (1) the development of the urinary concentrating mechanism during the postnatal period; (2) the cellular mode of action of vasopressin; and (3) mechanisms whereby urine can be concentrated in the absence of vasopressin. In the neuroendocrine field, questions include: (4) the biosynthesis and metabolism of neurohypophysial principles, including vasopressin, oxytocin, the neurophysins, and a search for the postulated precursor molecules; (5) phylogenetic and ontogenetic differences in the various neurohypophysial principles; and (6) the state of these principles in nephrogenic diabetes insipidus, as exemplified in mice with inherited forms of this disease. In many of the proposed experiments, three approaches --physiological, biochemical, and anatomical -- will be applied to investigating a given problem. Methods and preparations will include: renal micropuncture and clearances; specific radioimmunoassays for vasopressin, oxytocin, and neurophysins; quantitative light and electron microscopy; freeze-fracture electron microscopy; immunohistochemistry; analytical and preparative discontinuous polycarylamide gel electrophoresis; chromatography; peptide mapping; digestion with enzymes; and amino acid analysis.